Study: Warming affects plant-growth cycles more than expected

Maybe you believe in global climate change, or maybe you don’t, but some scientists have moved on from the question of its existence to studying its potential effects. In a study reported in this month’s edition of the journal Nature, researchers from 20 institutions in North America and Europe analyzed data from observational studies and warming experiments spanning four continents and 1,634 plant species using a common measure of temperature sensitivity.

The researchers tracked long-term observations measuring the actual change, in nature, in the timing of life events such as flowering, and calculated the change in days per degree Celsius of temperature change. They compared those observations with results of experiments using controlled environments designed to simulate climate change – the more common method for estimating plant response to climate change.

The researchers concluded that that warming experiments under-predict advances in the timing of flowering by 8.5-fold and leafing by 4-fold compared with long-term observations.

Data from the controlled experiments predict that each degree Celsius in higher temperatures would advance plants' flowering and leafing from half a day to 1.6 days. Based on observations in nature however, the researchers found these events actually advanced five to six days, on average, per degree Celsius.

In a news release, the researchers say global land surfaces have warmed an average of about half a degree Celsius (1.25 degrees Fahrenheit) over the past century. But some places are warming much more rapidly, such as Alaska, where temperatures have risen by about 1.8 degrees C, or over 3 degrees F. Long-term historical records show that many plant species are flowering and leafing out days or even weeks earlier than in the past. They note that the well-recorded blooming of Washington D.C.'s cherry blossoms has advanced about a week since the 1970s. If the trend continues at the same rate, projections suggest that by 2080 the trees will be blooming in February. They also note that animals react to the change, saying, for example, that robins are returning to the Colorado Rockies a month earlier than they did in the early 1970s.

Institutions participating in the study include the University of California – San Diego, NASA Goddard Institute for Space Studies, Lamont-Doherty Earth Observatory, Palisades, New York, the University of Connecticut, US Geological Survey, North Dakota State University and several others.

An abstract and paid access to the full article are available from Nature.